A dispersive solid phase extraction method combined with reversed phase liquid chromatography was investigated for the determination of benzo ( a ) pyrene ( BaP ) residues in edible oil and oil products. The developed “one-step” sample preparation method integrated with the adsorbent activation, sample extraction and sample cleaning. Using Alumia-N as the adsorbent, good cleaning effect and high recovery ranging from 81. 5% -97. 5% was achieved. In addition, coupled with fluorescence detector (FLD), high sensitivity was obtained with LOD of 1. 0 μg/kg (S/N=3). Furthermore, SPSS was used to design orthogonal optimization experiments and establish the optimal condition. Under the optimized condition, the standard calibration curve was linear over the concentration range of 0. 5-10. 0μg/L, with the regression efficiency (R2) of 0. 9997. The relative standard deviation (RSD) of peak area was between 2. 6%-4. 9%, showing good repeatability and the reliability.

An automated analytical method for simultaneous determination of vitamin A and E in livers, fortified infant formulae and eggs has been developed based on on-line solid phase extraction (SPE) coupled with a dual gradient high performance liquid chromatography system with column-switching. Firstly, food samples were centrifuged after saponified in mixture solution of anhydrous alcohol, potassium hydroxide and ascorbic acid at 80 ℃ for 30 min. Secondly, the saponified sample was loaded and washed on the first dimension extraction column using methanol-water (60∶40, V/V). Afterwards, the targeted analytes were trapped and enriched on the SPE column. Finally, the trapped analytes were transferred to the second dimension analysis column by valve-switching technique for the following separation and determination. Several key factors such as the type of SPE columns, elution buffer as well as pH of washing solution were optimized. The results showed that the calibration curves of vitamin A and E were linear in the range of 0 . 02-20 mg/L with correlation coefficient (R2) more than 0. 9998. In addition, the limits of detection (S/N=3) were found in the range of 3. 0-30. 0 μg/L. The spiked recoveries of the vitamin A and E from livers, eggs and fortified infant formulae ranged from 87 . 3% to 115 . 0% with the relative standard deviations ( RSDs ) of 1 . 8% -4 . 6%. The developed method is simple, sensitive and rapid to determine vitamins A and E in animal derived food.

A method for determination of residues of 26 β2-agonists in pork liver was developed using high performance liquid chromatography with tandem mass spectrometric ( HPLC-MS/MS ) . After enzymatic hydrolysis with β-Glucuronidase/Arylsulfatase for 12 hours, the pH of sample solution was adjusted to 1 using perchloric acid for protein precipitation. The precipitate was extracted with 0. 1mol/L perchloric acid aqueous. The extracts in the above two steps were combined and adjusted to pH 4 for the solid phase extraction ( MCX) . And then the 26 β2-agonists residues in the extracts were separated on a reversed phase HPLC column using a gradient elution program of 0. 1% formic acid aqueous solution (A) and 0. 1% formic acid in acetonitrile solution ( B) . Multiple reaction monitoring ( MRM) with positive polarity was selected to monitor qualitative and quantitative ion. Based on the optimized method, 26 β2-agonists could be analyzed in 15 min. The recoveries ranged from 64 . 0% to 112 . 7% for the 26 kinds ofβ2-agonists residues with three spiked levels of 5, 10 and 20 μg/kg. The relative standard deviations ( RSDs) were less than 15. 2%. The limits of detection (LOD) for the 26 kinds of β2-agonists were 0. 15-1. 35 μg/kg.